Project Abstract Motivation: This is a competing renewal of our successful project Rapid Robust Pediatric MRI, R01 EB009690. MRI offers superb soft tissue contrast and high resolution for children, without the ionizing ra- diation and cancer risk of CT. However, its use has been limited as children often cannot voluntarily suspend respiration or tolerate long exams. MRI often requires anesthesia with attendant risk; hence, children often lack the bene?ts of cross-sectional imaging altogether or are exposed to ionizing radiation. The previous project addressed these concerns by creating a dedicated pediatric imaging system. Highly par- allel, high SNR 3T receive arrays were designed and constructed speci?cally for pediatric body imaging. The high SNR was used to accelerate scans reconstructed with a combination of parallel imaging, new motion correction algorithms, and compressed sensing (CS). Parallel computing reconstruction algorithms produced 3D volumes in 1 minute. The resulting system is being used extensively in clinical practice, signi?cantly reduc- ing anesthesia, and has markedly increased our abdominal MRI utilization. Key technologies are now being commercialized with GE Healthcare, including the pediatric receive array, CS, and coil compression. Despite signi?cant progress, with markedly reduced scan times, anesthesia has not been eliminated. Patient motion remains the main limitation. Therefore the major emphasis here is addressing motion through robust imaging, motion correction, and dynamic MRI. This will (1) extend the bene?ts of MRI to younger, less co- operative patients, (2) allow the correction and depiction of respiratory motion, and (3) provide the temporal resolution that captures the faster contrast dynamics in children for free-breathing 3D dynamic studies. Approach: The project has three interrelated development aims, validated by clinical studies. Aim 1 is to enable robust acquisition and reconstruction in the presence of motion in 3D studies. This uses robust parallel imaging calibration and reconstruction, outlier insensitive optimization and a new approach for measuring localized nonrigid motion throughout the body using array coil elements. A second aim is to develop ultrafast multi band 2D approaches for faster imaging of uncooperative patients. This freezes motion in each set of slices, simplifying motion correction over the volume. The impact of these developments in the clinic will then be assessed in the setting of appendicitis, a representative common and challenging pediatric abdominal imaging application. Then we will exploit temporal correlations and dynamics in time-resolved 3D contrast studies and further speed 2D scans, and again assess the impact in children with suspected appendicitis. Signi?cance: This work will lead to fast, robust, broadly-applicable pediatric body MRI protocols with less anesthesia, making MRI safer, cheaper, and more available to children, transforming it into a workhorse modality and decreasing CT radiation burden. The techniques will facilitate wide application in the community setting and permit new MRI applications, for both pediatric and adult disease.